[ATM] Grinding the back flat

[Jason Hissong <jhissong@gmail.com>]

Hello again,

Thanks to those who responded on the ROC being to short.  The strokes 
Bob provided seemed to be doing the trick.

My next question is grinding the back flat.  Why do I ask now after I 
have grinded some already?  Well, I thought I already did grind it flat 
enough, but it appears that it does rock back and forth slightly in one 
axis.  So I am going to work the back more until I don't feel any rocking.

A couple of questions:

To grind it flat, I know you can use window glass to do that.  I don't 
have any so I had a 6" tile tool that was going to be used to grind a 6" 
mirror.  It ended up not being used and the surface is flat.  Will this 
be adequate (using W strokes or something).

Being that I discovered the rocking after about 3 hours worth of 
grinding (some at 120 and some at 220), how long would it take to grind 
out any astigmatism that is in there.  Is there a way to measure this?  
Did not know if going down the finer grits (starting at 25 down to 5) 
would eventually get the astigmatism out.

Oh yea, the wife gave me permission to get a telekit once the 14" is 
done and polished...  In fact, she thought that was a better idea than 
doing it from scratch.  I asked her who she was and where was my wife!  
I am working on the 8" now, but the 14" will be next.

Clear Skies,

Jason
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